scholarly journals Dapagliflozin Exerts Adrenal Sympatholysis via G protein-Coupled Receptor Kinase-2 & Tyrosine Hydroxylase Downregulation

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A655-A655
Author(s):  
Anastasios Lymperopoulos ◽  
Celina M Pollard ◽  
Daniela Pi Noa ◽  
Krysten E Ferraino ◽  
Natalie Cora ◽  
...  
Keyword(s):  
Tyrosine Hydroxylase ◽  
G Protein ◽  
Radioligand Binding ◽  
Treated Animal ◽  
Receptor Kinase ◽  
Sprague Dawley ◽  
G Protein Coupled Receptor ◽  
Neurogenic Hypertension ◽  
G Protein Coupled

Abstract The sodium-glucose co-transporter (SGLT)-2 inhibitor dapagliflozin was recently reported to reduce renal tyrosine hydroxylase (TH) and norepinephrine levels, lowering blood pressure and preventing endothelial dysfunction, in a murine model of neurogenic hypertension. This suggested that dapagliflozin may combat sympathetic nervous system (SNS) hyperactivity, which is known to accompany and aggravate chronic heart failure (CHF). Adrenal G protein-coupled receptor kinase (GRK)-2 upregulation is a major driver of circulating catecholamine (CA) elevation and SNS hyperactivity, especially in CHF. GRK2 severely dysregulates adrenal sympatho-inhibitory α 2-adrenergic receptors (ARs), leading to unchecked, chronically elevated CA secretion. Therefore, we hypothesized herein that SGLT2 inhibition with dapagliflozin may lower SNS hyperactivity in the adrenal gland by antagonizing GRK2 actions on α 2ARs in adrenal chromaffin cells. We used the rat pheochromocytoma PC12 cell line expressing human α 2AAR, as well as freshly isolated adrenal glands from adult male Sprague-Dawley rats treated with dapagliflozin in vivo. We measured circulating norepinephrine (NE) in vivo via RIA, GRK2 & TH expression levels via real-time PCR and immunoblotting, adrenal α 2AR density (Bmax) via saturation radioligand binding with [methyl-3H]-rauwolscine, and G protein activation via the GTPγS assay. Dapagliflozin treatment for 7 consecutive days (20 mg/kg/d in drinking water) led to a significant reduction in blood circulating NE levels (217+67 pg/ml, n=6), compared to control, vehicle-treated rats (363+77 pg/ml, n=6, p<.05), suggesting reduced SNS activity. This was accompanied by reduced GRK2 and TH mRNA and protein levels in dapagliflozin-treated rat adrenals vs. vehicle-treated animal-derived glands, indicating reduced adrenal CA synthesis and secretion. Finally, adrenal α 2AR density was higher in dapagliflozin- vs. vehicle-treated rats (51.3+7.3 vs. 26.1+8.1 fmol/mg of protein, respectively; n=12 glands from 6 animals per group, p<.05). These results (i.e. GRK2 and TH downregulation) were completely recapitulated in PC12 α 2AAR-expressing cells in culture, treated with 5 μM dapagliflozin (or vehicle) for 24 hours. Importantly, α 2AR-dependent G protein-mediated signaling towards inhibition of CA secretion was markedly enhanced at 24 hrs post-dapagliflozin application in PC12 cells. This was the result of reduced GRK2-dependent receptor desensitization, since dapagliflozin lacked this effect in cells co-transfected with a GRK2-encoding adenovirus to acutely overexpress GRK2. In conclusion, dapagliflozin exerts a sympatholytic action in the adrenal medulla via downregulation of both TH, which reduces CA biosynthesis, and GRK2, which reduces α 2AR desensitization in favor of enhanced inhibition of CA secretion.

scholarly journals Role of Endothelial G Protein-Coupled Receptor Kinase 2 in Angioedema

Hypertension ◽  
2020 ◽  
Vol 76 (5) ◽  
pp. 1625-1636 ◽  
Author(s):  
Jessica Gambardella ◽  
Daniela Sorriento ◽  
Maria Bova ◽  
Mariarosaria Rusciano ◽  
Stefania Loffredo ◽  
...  
Keyword(s):  
Vascular Permeability ◽  
G Protein ◽  
Molecular Mechanisms ◽  
No Production ◽  
Receptor Kinase ◽  
Severe Phenotype ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

Excessive BK (bradykinin) stimulation is responsible for the exaggerated permeabilization of the endothelium in angioedema. However, the molecular mechanisms underlying these responses have not been investigated. BK receptors are Gq-protein-coupled receptors phosphorylated by GRK2 (G protein-coupled receptor kinase 2) with a hitherto unknown biological and pathophysiological significance. In the present study, we sought to identify the functional role of GRK2 in angioedema through the regulation of BK signaling. We found that the accumulation of cytosolic Ca 2+ in endothelial cells induced by BK was sensitive to GRK2 activity, as it was significantly augmented by inhibiting the kinase. Accordingly, permeabilization and NO production induced by BK were enhanced, as well. In vivo, mice with reduced GRK2 levels in the endothelium (Tie2-CRE/GRK2 fl+/fl − ) exhibited an increased response to BK in terms of vascular permeability and extravasation. Finally, patients with reduced GRK2 levels displayed a severe phenotype of angioedema. Taken together, these findings establish GRK2 as a novel pivotal regulator of BK signaling with an essential role in the pathophysiology of vascular permeability and angioedema.

scholarly journals Receptor-specific in vivo desensitization by the G protein-coupled receptor kinase-5 in transgenic mice.

1996 ◽  
Vol 93 (18) ◽  
pp. 9954-9959 ◽  
Author(s):  
H. A. Rockman ◽  
D. J. Choi ◽  
N. U. Rahman ◽  
S. A. Akhter ◽  
R. J. Lefkowitz ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
G Protein ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

scholarly journals G-protein coupled receptor kinase 5 mediates lipopolysaccharide-induced NFκB activation in primary macrophages and modulates inflammation in vivo in mice

2011 ◽  
Vol 226 (5) ◽  
pp. 1323-1333 ◽  
Author(s):  
Sonika Patial ◽  
Shipra Shahi ◽  
Yogesh Saini ◽  
Taehyung Lee ◽  
Nandakumar Packiriswamy ◽  
...  
Keyword(s):  
G Protein ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

scholarly journals Hypothesis

2016 ◽  
Vol 22 (1) ◽  
pp. 51-53 ◽  
Author(s):  
Jonathan M. Powell ◽  
Emanuel Ebin ◽  
Steven Borzak ◽  
Anastasios Lymperopoulos ◽  
Charles H. Hennekens
Keyword(s):  
G Protein ◽  
Wall Thickness ◽  
Basic Research ◽  
Left Ventricular ◽  
Conditional Knockout ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

The hypothesis that paroxetine decreases morbidity and mortality in patients with heart failure (HF) is plausible but unproven. Basic research demonstrates that inhibition of G protein-coupled receptor kinase 2 (GRK2) both in vitro and in vivo in the myocardium may be beneficial. G protein-coupled receptor kinase 2 antagonism is purported to exert cardioprotective effects immediately following myocardial injury by blunting toxic overstimulation on a recently injured heart. In addition, chronic overexpression of GRK2 inhibits catecholamine induction of vital positive chronotropic and ionotropic effects required to preserve cardiac output leading to worsening of congestive HF. In cardiac-specific GRK2 conditional knockout mice, there is significant improvement in left ventricular wall thickness, left ventricular end-diastolic diameter (LVEDD), and ejection fraction (EF) compared to controls. Paroxetine is a selective serotonin reuptake inhibitor which was recently shown to have the ability to directly inhibit GRK2 both in vitro and in vivo. At physiologic temperatures, paroxetine inhibits GRK2-dependent phosphorylation of an activated G-protein-coupled receptor with a half maximal inhibitory concentration of 35 micromoles, a substantially greater affinity than for other G protein-coupled receptor kinases. In a randomized trial in mice with systolic HF and depressed EF postmyocardial infarction, those treated with paroxetine had a 30% increase in EF, improved contractility, and LVEDD and wall thickness compared to those treated with medical therapy alone. While further basic research may continue to elucidate plausible mechanisms of benefit and observational studies will contribute important relevant information, large scale randomized trials designed a priori to do so are necessary to test the hypothesis.

scholarly journals Inhibition of vascular smooth muscle G protein-coupled receptor kinase 2 enhances α1D-adrenergic receptor constriction

2008 ◽  
Vol 295 (4) ◽  
pp. H1695-H1704 ◽  
Author(s):  
Heather Irina Cohn ◽  
David M. Harris ◽  
Stephanie Pesant ◽  
Michael Pfeiffer ◽  
Rui-Hai Zhou ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
G Protein ◽  
Adrenergic Receptor ◽  
Plasma Norepinephrine ◽  
Mrna Levels ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled

G protein-coupled receptor kinase 2 (GRK2) is a serine/theorinine kinase that phosphorylates and desensitizes agonist-bound G protein-coupled receptors. GRK2 is increased in expression and activity in lymphocytes and vascular smooth muscle (VSM) in human hypertension and animal models of the disease. Inhibition of GRK2 using the carboxyl-terminal portion of the protein (GRK2ct) has been an effective tool to restore compromised β-adrenergic receptor (AR) function in heart failure and improve outcome. A well-characterized dysfunction in hypertension is attenuation of βAR-mediated vasodilation. Therefore, we tested the role of inhibition of GRK2 using GRK2ct or VSM-selective GRK2 gene ablation in a renal artery stenosis model of elevated blood pressure (BP) [the two-kidney, one-clip (2K1C) model]. Use of the 2K1C model resulted in a 30% increase in conscious BP, a threefold increase in plasma norepinephrine levels, and a 50% increase in VSM GRK2 mRNA levels. BP remained increased despite VSM-specific GRK2 inhibition by either GRK2 knockout (GRK2KO) or peptide inhibition (GRK2ct). Although βAR-mediated dilation in vivo and in situ was enhanced, α1AR-mediated vasoconstriction was also increased. Further pharmacological experiments using α1AR antagonists revealed that GRK2 inhibition of expression (GRK2KO) or activity (GRK2ct) enhanced α1DAR vasoconstriction. This is the first study to suggest that VSM α1DARs are a GRK2 substrate in vivo.

scholarly journals Modulation of Adrenal Catecholamine Secretion by In Vivo Gene Transfer and Manipulation of G Protein–coupled Receptor Kinase-2 Activity

2008 ◽  
Vol 16 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Anastasios Lymperopoulos ◽  
Giuseppe Rengo ◽  
Carmela Zincarelli ◽  
Stephen Soltys ◽  
Walter J Koch
Keyword(s):  
Gene Transfer ◽  
G Protein ◽  
Catecholamine Secretion ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
G Protein Coupled ◽  
In Vivo Gene Transfer

scholarly journals β-Arrestin 1 and 2 and G Protein-Coupled Receptor Kinase 2 Expression in Pituitary Adenomas: Role in the Regulation of Response to Somatostatin Analogue Treatment in Patients With Acromegaly

Endocrinology ◽  
2013 ◽  
Vol 154 (12) ◽  
pp. 4715-4725 ◽  
Author(s):  
Federico Gatto ◽  
Richard Feelders ◽  
Rob van der Pas ◽  
Johan M. Kros ◽  
Fadime Dogan ◽  
...  
Keyword(s):  
G Protein ◽  
Pituitary Adenomas ◽  
Somatostatin Analogue ◽  
Receptor Kinase ◽  
G Protein Coupled Receptor ◽  
Sstr Subtype ◽  
G Protein Coupled ◽  
Grk2 Expression

Recent in vitro studies highlighted G protein-coupled receptor kinase (GRK)2 and β-arrestins as important players in driving somatostatin receptor (SSTR) desensitization and trafficking. Our aim was to characterize GRK2 and β-arrestins expression in different pituitary adenomas and to investigate their potential role in the response to somatostatin analog (SSA) treatment in GH-secreting adenomas (GHomas). We evaluated mRNA expression of multiple SSTRs, GRK2, β-arrestin 1, and β-arrestin 2 in 41 pituitary adenomas (31 GHomas, 6 nonfunctioning [NFPAs], and 4 prolactinomas [PRLomas]). Within the GHomas group, mRNA data were correlated with the in vivo response to an acute octreotide test and with the GH-lowering effect of SSA in cultured primary cells. β-Arrestin 1 expression was low in all 3 adenoma histotypes. However, its expression was significantly lower in GHomas and PRLomas, compared with NFPAs (P < .01). GRK2 expression was higher in PRLomas and NFPAs compared with GHomas (P < .05). In the GHoma group, GRK2 expression was inversely correlated to β-arrestin 1 (P < .05) and positively correlated to β-arrestin 2 (P < .0001). SSA treatment did not affect GRK2 and β-arrestin expression in GHomas or in cultured rat pituitary tumor GH3 cells. Noteworthy, β-arrestin 1 was significantly lower (P < .05) in tumors responsive to octreotide treatment in vitro, whereas GRK2 and SSTR subtype 2 were significantly higher (P < .05). Likewise, β-arrestin 1 levels were inversely correlated with the in vivo response to acute octreotide test (P = .001), whereas GRK2 and SSTR subtype 2 expression were positively correlated (P < .05). In conclusion, for the first time, we characterized GRK2, β-arrestin 1, and β-arrestin 2 expression in a representative number of pituitary adenomas. β-Arrestin 1 and GRK2 seem to have a role in modulating GH secretion during SSA treatment.

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